<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
    .box {
        background-color: yellow;
        height: 600px;
        display: flex;
        /* flex-direction: column; */
        /* flex-wrap: wrap; */
        /* justify-content: center; */
        /* align-items: stretch; */
    }

    .item {
        width:200px;
        height: 200px;
        background-color: orange;
        font-size:30px;
        margin: 10px;

        flex: 1;
    }

    .two {
        flex: 3; 
    }
    </style>
</head>
<body>
    
    <div class="box">
        <div class="item">1</div>
        <div class="item">2</div>
        <div class="item two">3</div>
    </div>
</body>
</html>